In many types of fluid systems, and particularly in many refrigeration and air conditioning systems, the tubes (also referred to as pipes, conduits or hoses) in the system are connected together by suitable couplings of various types. In vehicle air conditioning systems, a common practice had been to provide the tube ends with a fitting that involved turning a threaded fastener disposed coaxially on the tube to connect the tube to another component. Drawbacks associated with such type of fitting included difficulty in turning the fastener, such as a nut, in a crowded engine compartment, the risk of damage to a seal or seals used with the fitting due to over tightening or leakage due to under tightening, and twisting of the tube during tightening.
Various coupling configurations have been devised to eliminate one or more of these drawbacks. Notwithstanding, there remains a continuing need to provide improved tube couplings that, among other things, reduce the escape of the fluid from the system at the coupling. This is especially important in air conditioning systems, where it is desired to minimize the amount of refrigerant that escapes to the atmosphere through the coupling.